1. Field of the Invention
The present invention relates to a regenerative refrigerator, a first stage regenerator, and a second stage regenerator.
2. Description of the Related Art
A regenerative refrigerator is used to cool an object to a temperature ranging from about 100 K (Kelvin) to about 4 K. A regenerative refrigerator is exemplified by a Gifford-McMahon (GM) refrigerator, a pulse tube refrigerator, a Stirling refrigerator, and a Solvay refrigerator. A regenerative refrigerator is used to cool a superconducting magnet or a detector or used in a cryopump, etc. The refrigerating capacity of a regenerative refrigerator is determined by the heat exchange efficiency of a regenerator material.